Electrical circuit for producing coding pulses



June 10, 1952 P. SAGALYN 0 ELECTRICAL CIRCUIT FOR PRODUCING CODING PULSES Filed Oct. 19, 1945 NEG. BIAS INVENTOR. PAUL L. SAGALYN ATTORNE Y Patented June 10, 1952 2,600,262? I ELEeTmcAn'cmomr FORTPRODUCING GO'DI'NG PULSES P511111. sagaiyfi;omunsamins; assigiiior'jby m sne assignments, tj,t l'1'eUiji te51";States :3 asi'epfsented by thesecretary of War L Application-October 19, 1945,- Serial No.-623, i01 s Claim'si' (o1: m -cs0) The invention relates in general to pulse generatinglcircuits' and more particularly to a circuit for producing a-series of pips separated by predetermined time intervals. These pi'p's' may; for

example; be used to code a beacon transmitter.

Theoutpiit of'tlie beacon'tifansnii-tter usually coded so as to "permit an" interrogating station toidefritify the beacon? One 'of'the most'common methodsof cddingisknown'as range 'co'diiisi In this type of coding a series "of pulse's'feach' pulse separated'fby a predetermined time interval from the-preceding pulse, is sent out'byIthe beacon in response to a signal from the 'interrogatiii'station. These pulses" appear "onrne' screen of'a ing station," as separate pips at difieffitdisttinoes along the range" axis," It"is"an"object "of 'this invritionto "devise a simple "coding "means for modulatingthe output of afibeaecniransmiaer.

Inmany instances it necessary 'td' have a portable beacdn which 'canbe transported by "aircraft. In beacons of this type it is particularly desirable to have all the components compact, of light weigfifaridwith'lovv' power drain." It is accordingly a'further 'obict'of the 'invention'to' devise acircuit for anodihg component which will be com act; light in Weight; and have a low power firaiiii I Other objects and "advantages will become readily apparent fromthe hereinafter "described specification. I

The coder. circuit us'es""tlireej vacuum tubes. The twotub'es' areconneotedto "the source of 'anode'potential' through tank brriii'ginfcircliitsL E aLCh Of methree "tubes has'a Winding ofa blocking" oscillator transfer-finer anode circuit. Th'e'three tubes alsdhave' a co'minon cathode'resistor across whichthe positive coding pulses are developed; I I

The action of the coder is initiated by the appli'cation "of a positive pulse, through a blocking capacitor; to a grid of a "first tube. begins the blocking oscinawr 'actiorif'of the 'firsttube, which'drawsa sh'ort heavy pulse of "anode current; chargin g a capacitor tankbiitcuit. This heavy pulse of current flowing through a common cathode resistor also gives thefirst'cod- I mg pulse. The tank circuit capacitor at the same time will begin to discharge: through the inductance, and oscillations begin. The second tube is a. biased-off blocking oscillator arranged to fire on the rise of potentialdueto the oscillation of the first tankcircu'it." The time interval is approximately equal to one-half the natural period of-oscillation of the-tank circuit-.-- Thistimeinterval determines the spacing between codingpulses. As soon as-the'second-tubefires, apositive pulse appears across the common cathode resistor, and the tank circuit associatedwith I c and through a tan or ringing circus the secondtu-be-beiiis'to oscmate': Thethiid tube will fiie' as scones potential: dii' td'tfie oscillation ofthe tank "circuit." reaches" he 7 proper value and a third positivpiilse will appear across the cdrn i'rion cathode resi ns I No tank circuit isus'd the anod'ciiciiit of the third' tube since only thrfpiiisesardsired fromthe circuit shown; This circuit m'ay be-adapted to provide as man'y'pulse's as desired 10' by adding stages! This circuit-has a verygmw draiiibIi-th plate supply sincegall-the tubes are normally 'biased ofi and each'tube draws current only eunng as pulse.

15 In the drawing, rig-. 1 a diagrammatic view of the "preferred" embodiment I'of rny invention, and Fig1- 2 shows schematiailyythe wayeiqr ns ap earing atvarious points i-n'the circuitof Fig. 1 shows three'triodetype vacuumtubes, to

90 which --the-reference numerals I, '2 'and' 3- have 35 connected tofigroun'd-"at a common te'r minal'-E through the common cathode resistor 1'3 4 The anod of tube i i's'connected to thesource of anodepotentiai througli a terminal C'of a M of a blocking oscill'atdr transfdriner consisting-of acapacitor IG an'd inductance" 1-; The other winding 1 1 of-the transformr has one terminal conncted-tdthe grid of ube Z 'andthen to -a source of "negative -'poi'ieritiahrouli're's'istor B through blocking cap'acitorfit".

The'anode 'of'tube'3' is'conne'ctd era terminal D to the" source of anode" potential through the winding 2 I of blocking oscillator transformer 2 3.

. Thwinding24 of'the transformerhas'bneterminal connected to the grid and thgiitdjQ'sdiifie of I negative bias through resistor 2e. e" other terminal of the WindiiigFZA is connected through blocking capacitor-26 to'terfninalC.

The tubes' L2 and 3 are" normally biased a; cut

ofi by means or the negative"poteiinar p ntc'm the grids mmugnresstorss, 19* and 25"iesiie'c tivelyi The initial" trigger pulse; is?appliedfto terminal A from" anther" circuit (not slibtvtD The input impedance of the coder circuit should be designed to match the output impedance of the circuit supplying the trigger pulse.

If the coding circuit is used in a beacon, the trigger pulse will come from the discriminator which responds only to an R. F. beacon interrogating pulse of the proper frequency and duration.

The trigger pulse is applied at terminal A to the grid tube I through a blocking capacitor 5. This trigger pulse is shown in graph A of Fig. 2. The grid of this tube is connected to a source of negative potential through resistor 6. The positive pulse on the grid of tube 1 causes a sharp increase in anode current to be drawn through the winding 8. This pulse of current, appearing at terminal B and shown in graph B of Fig. 2, induces a pulse of voltage on the winding l l of the transformer I and initiates the blocking oscillator action. The heavy pulse of current, drawn by the tube during the blocking oscillator action, causes a positive pulse of voltage to appear at common terminal E across the common cathode resistor 13. This pulse of current, shown as the first pulse in graph E of Fig. 2, also charges capacitor 9 which starts to oscillate with inductance H1. The rise of potential at terminal B due to this oscillation is transmitted to the grid of tube 2 through capacitor 2|. Tube 2 will begin to conduct, initiating blocking oscillator action after a time interval equal to approximately half the natural period of oscillation of capacitor 9 and inductance H1. The tube 2 will draw a heavy pulse of current appearing at terminal C and shown in graph C of Fig. 2 due to blocking oscillator action, which also appears at terminal E across resistor 13 as a second pulse or pip which is spaced from the first pip by a time interval equal to the delay in the firing of tube 2. This second pulse is shown as the second pulse in graph E of Fig. 2.

The aforementioned second pulse of current charges capacitor [6 which begins to oscillate with inductance l1 and, after a time interval equal to approximately half the natural period of oscillation of capacitor l6 and inductance I1, tube 3 will begin to conduct, causing a current pulse to appear at terminal D, as shown in graph D of Fig. 2, and a third pip will appear across resistor l3. This third pip is shown as the third pulse in graph E of Fig. 2.

If the period of oscillation of capacitor 9 and inductance I is the same as for capacitor 16 and inductance I1, the interval between the first and second pips will be the same as between the second and third pips. The oscillations of the two tank circuits are damped by resistors l9 and 25 and the time of recovery for the tubes is sufficiently long so that they are triggered only once. The tubes will not fire again until a new trigger pulse is applied to terminal A. The length of the time interval between pips can be changed by using a different value for the capacitor or by changing the value of the negative bias.

The trigger pulses or pips from across resistor 13 may be used to fire a beacon transmitter either directly or through a modulator.

It will be apparent that there may be deviations from the invention as described which still fall fairly within the spirit and scope of the invention. For example negative pips may be obtained from the circuit by using a common resistor between the source of anode potential and the anodes of the three tubes.

Accordingly, I claim all such deviations which fall fairly within the spirit and scope of the invention as identified in the hereinafter appended claims.

What is claimed is:

1. An electric circuit for producing coding pulses comprising a first blocking oscillator pulse generator including a vacuum tube having an anode, a cathode, and at least one control grid, said tube being biased to cut-oil, means for applying unblocking pulses to the cathode-grid circuit of said first pulse generator, a load connected between said cathode and anode, a tank circuit connected between said cathode and anode, a second blocking oscillator pulse generator including a vacuum tube having a cathode, an anode, and at least one control grid, said last-mentioned tube being biased to cut-off, means coupling said tank circuit to the cathodegrid circuit of said second pulse generator for unblocking said second pulse generator during the second half of an oscillation of said tank circuit started by a pulse from said first pulse generator, and means coupling the output of said second pulse generator to said load.

2. An electric circuit for producing coding pulses comprising a first blocking oscillator pulse generator including a vacuum tube having an anode, a cathode, and at least one control grid, said tube being biased to cut-off, means for applying unblocking pulses to the cathode-grid circuit of said first pulse generator, 9. load connected between said cathode and a point of common potential, a tank circuit coupled between said anode and said point of common potential, a second blocking oscillator pulse generator in cluding a vacuum tube having a cathode, an anode and at least one control grid, said lastmentioned tube being biased to cut-ofi, means coupling said tank circuit to the cathode-grid circuit of said second pulse generator to unblock said second pulse generator during the second half of an oscillation of said tank circuit started by a pulse from said first pulse generator, and means coupling the cathode of said second pulse generator to said load.

3. A circuit according to claim 2 further comprising a third blocking oscillator pulse generator including a vacuum tube having a cathode, an anode, and at least one control grid, said last-mentioned tube being biased to cutoff, a second tank circuit connected between the anode of the vacuum tube of said second pulse generator and said point of common potential and coupled to the cathode-grid circuit of said third pulse generator to unblock said third pulse generator during the second half of an oscillation of said second tank circuit started by a pulse from said second pulse generator, and means coupling the cathode of the vacuum tube of said third pulse generator to said load.

PAUL L. SAGALYN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,076,335 Dallenbach Apr. 6, 1937 2,277,000 Bingley Mar. 17, 1942 2,398,771 Compton Apr. 23, 1946 2,409,229 Smith Oct. 15, 1946 2,421,606 Fitch June 3, 1947 

